Conversion of hydrocarbon oils



April 4,1939.

L. A. MEKLERy CONVERSION 0F HYDROCARBON OILS Filed June 15, 1935 |NvENToR LEY A. MEKLER muZmUmm Patented pr. 4, 1939 PATENT OFFICE aiszsus Y ooNvnasroN or mmaooaanon Vmns Lev A. Makler, Chicago. Ill., as signor to Universal Oil Products Company, Chicago, Ill., acorporation of Delaware Application .rune 1s, 1935, serai Naasssz v s cnam.` (o1. 19e-ss) This invention refers to an improvedprocess and apparatus for the conversion of relatively low-boiling hydrocarbon oils such as, for example, gasoline, naphtha and other distillates containing 5 a substantial quantity of materials within the boiling range of motor fuel.

Cracking operations of the type above mentioned which are ordinarily termed reforming.

` operations generally employ a "soaking section in the heating coil to which they are supplied for conversion, in which soaking section the oil, which has been previously heated to a. high conversion temperature, is maintained for'an appreciable predetermined time at a substantially constant .temperature near that previously attained. Re-

forming operations, as now commonly practiced, differ from ordinary high-pressure cracking operations employing a tube and chamber type of system in three respects, namely, the higher temperatures and pressures to which the oil is subjected in the heating coil', the appreciably greater length of time during which the oil is subjected to conversion conditions in the heating coil and the factthat, in the best reforming operations.

further conversion of the oil after it leaves the heating coil is arrested by one or more of several methods of cooling. While'the conversion temperatures employed for reforming are, in many cases, within th range of those employed in vapor-phase cracking operations the reforming type of operation differs from the vapor-phase type principally with ,respect to the high superatmospheric pressure employed in the former and also with respect to the greater conversion time normally employed by the former. i The use of a "soaking section such as above referred to necessitates a large furnace to accommodate the relatively long length of heating coil requiredfor the soaking section and due to the fact that the temperature of the oil is not ordinarily increased more than or thereabouts, above the temperature attained in the preceding portion of the heating coil, the soaking section of the furnace and heating coil employs Irelatively 45 low rates of heat input. Another disadvantage in this method of operation resides in the fact that any heavy residual liquid and polymerization products formed in the heating coil are required to remain therein for the same length of time as 5 lower boiling products (which are substantially in vaporous state in the soaking section). This necessitates careful selection of the charging stock and accurate control of theheatlng conditions in order to avoid the excessive kformation and depositionof coke in the heating coil.

The present invention obviates both of the disadvantages above mentioned, which are common to present reforming operations, by employing i an enlarged externally heated chamber maintained at substantially the same pressure as that 5 employed in the heating coil in place of the soaking section of the heating coil. The use of an enlarged chamber as the soaking section in this type of operation offers several distinct advantages over the use of a soaking section comprising 10 an elongated tubular conduit of relatively small cross-section within a furnace. Separation of residual liquid and heavy polymerization products and removal of these materials from the cracking zone, without permitting their appreciable fur- 15 ther conversion and coke formation, is readily accomplished in a chamber but notin a continuous coil. considerably less pressure drop is encountered in the enlarged chamber than in a continuous soaking coil of the same cracking capacityl 20 so thatan appreciably smaller pressure, as measured at the inlet to the heating coil, is required for maintaining the pressure in a soaking chamber the same as that in a soaking coil. By eliminating the elongated tubular soaking coil the size 25 of the furnace required is, of course, greatly decreased and high rates of heating may be. employed throughout the furnace and heating coil. The desirability of employing high rates of heating in the heating coil and the fact that a 3o relatively large volume of relatively high temperature combustion gases offer an ideal means for externally heating the soaking chamber. make the process of the present invention particularly well suited to the use of a modern type of heater of relatively small size wherein high rates of heating and high tube efficiency` is obtained by radiation from materials undergoing combustion and the hot refractory walls of the furnace to opposite sides of each tubular element of the fluid 'o` conduit. Relatively large volumes of relatively high temperature flue gases are obtained from this type of furnace when convection or economizer sections are not employed in conjunction withV the radiant heating sections and, in the preferred embodiment of the present invention, flue gases from this type of furnace are utilized as a' means of externally heating the soaking chamber and, as another feature of the invention, the oil supplied to the heating coil may be preheated, prlor to its v introduction thereto, by indirect heat exchange with the combustion gases after their contact with the external walls of the soaking chamber, thereby decreasing the load on .the furnace. decreasing the temperature of the u ing eiciency obtained in the operation.

rI'he accompanying diagrammatic drawing illustrates one specific form of apparatus embodying the features of the present invention. Referring to the drawing, hydrocarbon oil charging stock for the process is supplied-through line I and valve 2 to pump 3 by means of which it is fed through line 4 and may be directed, all or in part, through line 5, valve 6, heat exchanger 1, line 8, valve 9, line III, line II valve I2, preheating coilI3, line I4 and valve I5 back into line I0 and thence to heating coil I6. The charging stock is preheated in heat exchanger 1 by indirect heat exchange with hot reflux condensate from the fractionator of the system and in preheating coil I3 with combustion gases having passed over the external walls of the soaking chamber. These preheating operations will be later more fully described. All or a portionv of thecharging stock may by-pass heat exchanger 1 by means of valve I1 in line I0 and valve I8 in this line permits the charging stock to by-pass preheating coil I3, all or in part, when'desired.

Heating coil I6, wherein the oil to be subjected to conversion within the lprocess is heated to the desired relatively high conversion temperature, is located Within a furnace I1 of any suitable form and, in the particular case here illustrated, this zone is of the type wherein high rates of heating are imparted .to the heating coil and to the oil passing therethrough by direct radiation from the flames. combustion gases andhot refractory walls of the furnace to opposite sides of each of the tubular elements I8 of the fluid conduit. In the particular case here illustrated a single tube bank, comprising two vertically parallel rows of horizontally disposed tubes I8, is centrally located between combustion vzone I9 and combustion zone 20 of the furnace,

the tubes in the two rows being arranged in staggered formation so that opposite sides of each tube are exposed to direct radiation. Combustion zones I9 and 20 are each supplied by means of suitable burners 2I with controlled amounts of combustible fuel and lair and the burners are preferably directed at anangle toward the side walls of the furnace so that the walls are washed bythe flames and thereby heated to a highly radiant condition. I'his also avoids excessive washing of the tubes by the hot combustion gases and prevents impingement of the flames against the tubes. The combustion gases are removed through suitable openings 22 in the floor of the furnace to ue23 from which they may be directed through flue 24 controlled by a damper 25 to a stack, not shown, or preferably they are directed, allor in part, from flue 24 through duct 25 controlled by damper 26 to the furnace setting or jacket 21 which encloses soaking chamber 30, as will be later more fully described. The oil is heated to ay relatively high conversion temperature as it passes through heating coil I6 and the hot conversion products are discharged from the heating coil {,)hroxsiugh line 28 and valve 29 into soaking cham- Chamber 30 'is an enlarged externally heated chamber replacing what is commonly termed the soaking section of heating coils' of the type normally employed in reforming operations and isvpreferably operated at substantially the same pressure as that employed at the outlet from heating coil I6. A .sufliciently -high temperature is maintained around the soaking chamvinal glue gases and increasing the ,overall heatber to keep the vaporous conversion products at or near the maximum temperature attained in thel'heating coil. This is accomplished, in the case here illustrated, by supplying hot combustion gases to the annular space surrounding the soaking chamber enclosed by a furnace setting or :jacket 21 of any suitable form.

Provision is made, as previously described, for supplying a regulated portion or all of the hot combustion gases from furnace I1 to the heating zone surrounding the soaking chamber and provision is also made for supplying fresh combustion products to this zone by means of the combustion of fuel of any suitable form supplied by a suitable burner 3i to duct 25. These fresh combustion products may serve to augment and A increase the temperature of the flue gases from furnace I1 when required or the soaking chamber may, when desired, be heated entirely by the fresh combustion gases without employing ue gases from furnace I1, although this is not the preferred method of operationof the process.

In case it is desired to cool the com bustion gases, prior to their introduction into the heating zone surrounding the soaking chamber, provision is made for supplying controlled amounts of air to duct 25 by means of suitable air inlet doors 32.. One or a plurality of suitable checker walls 33 in duct 25 may be employed, when desired, to effect mixing of the combustion gases and air or ofthe flue gases and fresh combustion gases, prior to their introduction into the heating zone surrounding the soaking chamber. In the particular case here illustrated the heating gases are tangentially supplied through duct 25 to the heating zone surrounding the 4 soaking chamber and a helical baille 34 of suitable metal,

metallic alloy or refractory material is provided in this zone in order to increase the path of travel and the velocityA of the heating gases around the .soaking chamber, thereby increasing the heat input through the chamber and also insuring better distribution of heat around the chamber.

Another method of partially cooling the combustiongases from furnace I1 to the desired temperature, prior to their contact with chamber 30, which is entirely within the scope of the pres,- ent invention, although not illustrated, comprises disposing a suitable heating coil in the flue connecting furnace I1 with furnace 21, for preheating the oil supplied to heating coil I6 or for any other desiredl purpose, or, when desired,

' an air preheater, not illustrated, for preheating version products in the soakingf zone, although provision for only concurrent flow is illustrated in the drawing. This maybe accomplished by introducing the heating gases into the upper portion of furnace 21 and withdrawing the same from the lower portion thereof, by well known means not shown, `the heated products from heating coil lbeing supplied to the lower por tion of chamber 30, as illustrated. This method of operation is particularly advantageous in case it is desired to employ a substantially uniform vapor temperature in chamber 30 and it also tends to avoid any excessive heating in this zone of the heavy liquid conversion products which collect in the lower portion thereof. In case a higher initial temperature and/cr a decreasing vapor temperature is desired in the chamber 30 concurrent flow of vapors and heating gases isv preferably employed in the soaking zone.

The heating gases, after their passage around chamber 30, are directed through flue 45 to a suitable stack, not shown, and, in accordance with the embodiment of the invention here illustrated, these gases are directed over a suitable preheating coil i3 to which oil subsequently supplied for conversion to heating coil I6 is directed, as previously described,- recovering heat therein from the ilue gases.

It is also Within the scope of the inventionto supply any quantity of the combustion gases from furnace I1, which are not supplied to furnace 21 directly to ilue 45 to commingle with the gases from furnace 21 prior to their contact with preheating coil i3, thereby supplying additional heat to this zone andutilizing the waste heat in that portion, if any, of the relatively hot combustlon gases from furnace-I1 not required for heating chamber 30. This may be accomplished by means of la continuation of ue 24 communiveating with flue 45 ahead of heating coil i3, although, for the sake of simplicity, 25

this provision is not shown in the drawing.

Chamber 30, in addition to its function as a soaking zone, serves as a zone of separation for the vaporous conversion products and any residual liquid and heavy polymerization products formed in heating cil i6 and/or chamber 30. The lower portion of chamber 30,`.in the case here illustrated, is insulatedbut unheated and the heavy liquid hconversion products may be momentarily collected within this zone and may be withdrawn therefrom through line 35 and valve 36 to cooling and storage or elsewhere, as desired, or preferably, this material is directed through line 31 and valve 38 to pump 39 by means of which it is supplied through line 40 and valve 4l to reduced pressure vaporizing chamber 44, which will be later more fully described.

The vaporous conversion products, after being subjected during theirpassage upward through chamber 30 to the relatively high conversion temperature maintained in this zone are withdrawn from the upper. portion thereof and directed through line 42 and valve 43 into chamber 44 preferably being cooled sufficiently, prior to their introduction into this zone, to prevent any substantial further conversion thereof. This cooling is preferably accomplished, at least in part, by substantial reduction in the pressure imposed upon the vaporous products as they pass through valve 43 in line 42 and in part, when desired, by other cooling means, which will be later more fully described. i

Reduced pressure vaporizing chamber '44 is, in the case here illustrated,v located within the lower portion of column 46; the upper portion of which comprises fractionator 41. Further sepa'- ration of any undesirable high-boiling polymerization products or `residual liquids from. the vaporous conversion products is accomplished in chamber 44 and when heavy liquids from chamber 30 are supplied to this zone, in the manner previously described, further vapori'zation thereof may be accomplished under the reduced pressure conditions maintained in chamber 44. 4The high-boiling liquid conversion products remaining unvaporized in chamber 44 may be withdrawn therefrom through line 43 and valve 43 tocooling and storage or elsewhere, as desired.

.The vaporous conversion products pass from the upper portion of chamber 44 through a suit- 75 able partition or deck ,which aeparatesthe vaporizing chamber from the fractionator, into fractionator 41 wherein their components boiling above the range of the desired nal motor fuel product of the process are condensed as reflux condensate. The reflux condensate may be allowed to collect within the lower portion of v fractionator 41 above partition. or deck 50 and is withdrawn' therefrom through line 5| and valve 52 to pump 53 by means of which it is fed through line 54 and may be returned, all or in part, through line 55, valve 56 and line l0 to heating coil I6 for further conversion or the hot reux condensate may be directed through valve 51 in line 64 to `heat exchanger 1, wherein it serves to preheat the charging stock by indirect heat exchangetherewith, as previously indicated. 'I'he partially cooled reflux condensate is' discharged from heat exchanger 'i through line 58,

and a regulated portion or all of these partially cooled products may, when desired. be directed through line 69 and valve 6i! back into fractionator 41 at any suitable point or plurality of points in this zone to serve as a cooling and reiiuxing medium. Preferably at least a portion of v fractionator 41 and are directed through line 65v and valve 66 to condensation and cooling in condenser 61. The. resulting distillate and gas i passes through line 68 and -valve 69 to collection and separation in receiver 10. Uncondensable gas may be released from the receiver through line 1I and valve 12. Distillate may be withdrawn from receiver through line 13 and valve 14 to storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver 10 may be recirculated, by well known means, not shown in the drawing, to the upper portion of fractionator 41 to serve as a cooling and reuxing medium in this zone for assisting fractionation ofthe vapors and to maintain the desired vapor outlet temperature from the fractionator.

The preferred' range of operating conditions which may be employed to accomplish the objects of the present invention in an apparatus such as illustrated and above described may be approximately as follows: 'I'he heating coil may employ an outlet conversion temperature ranging, for example, from 950 to 1050*' F., preferably at a superatmospheric pressure of the order of 300 to 800 pounds, or more, per square inch. The soaking chamber is preferably maintained at substantially the same pressure as that employed at 4the outlet from the heating coil and a converemployed at the outlet from the heating coil. A

substantially reduced pressure relative to thatl employed lin the soaking chamber is preferred in the succeeding vaporizingand separating chamber ranging, for example, from pounds, or

thereabouts, per square inch, down to substantially atmospheric pressure and this pressure may be substantially equalized or reduced in the'succeeding fractionating, condensing and collecting portions of the system. The temperature of the. conversion products supplied from the soaking chamber to the reduced pressure vaporizing chamber is preferably reduced to a temperature ranging, for example, from 600 to 800 F., or thereabouts, although this provision is not soessential to the successful operation of the process as in other reforming operations wherein no previous separation of vaporous and heavy liquid conversion products is accomplished. y v

As a specific example of the operation of the process of the present invention as it may be accomplished in an apparatus such as illustrated and above described, the charging stock, which comprises a Pennsylvania distillate of about 50 A.' P. I. gravity, is preheated by indirect heat exchangewith reux condensate from the fractionator of the system and by additional heating, in a preheating coil utilizing residual heat in the combustion gases from the heatngzone surrounding the soaking chamber, Ito a temperature of approximately 600` F. and is quickly heated in a heating coil and furnace of the type illustrated to an outlet conversion temperature of approximately 970 F. at a superatmospheric pressure of about 500 pounds per square inch. Combustion gases are withdrawn from the heating coil furnace at a temperature of approximately 1200 F. and are' circulated around the soaking chamber, serving to maintain the vaporous'4 products in this zone at an average temperature of. approximately 980 F. Heavy liquid conversion products are'withdrawn from the unheated lower portion of the soaking chamber and supplied to the reduced pressure vaporizing chamber to which the vaporous products from the soaking chamber are separately supplied afterbeing cooled by pressure reduction and by commingling with relatively cool reflux condensate from the fractionatorv to a temperature of approx imately '760 F., a superatmospheric pressure of approximately 100 pounds is` maintained in the vaporizlng and separating chamber and is substantially equalized in the succeeding fractionating, condensing and collecting portions of the system. This operation will produce, per barrel of charging stock, approximately 83 per cent of motor fuel having an'octane number of approximately 70 and a small amount of heavy residual liquid, the remainder being chargeable, principally. to uncondensable gas. I claim as my invention: 1. A reforming process which comprises pass ing a relatively low-boiling hydrocarbon oil dis- A tillate containing low anti-knock gasoline fractions in a continuous stream through a uid conduit within a furnace, quickly heating the oil during itspassage through the fluid conduit to a reforming temperature at substantial superata', mospheric pressure by heat supplied to the fluid conduit predominantly by radiation from ma-l terials undergoing combustion within the furnaceA and the hot refractory furnace walls, introducing the. highly. heated oil fromthe heating coil into the unheated lower portion of an enlarged vertical chamber, the upper portion of which is externally heated, separating the vaporous and' liquid conversion products in the lower portion of saidv chamber; withdrawing the latter therefrom, withdrawing hot combustion gases from said furnace after at` least `a maior portion of their radiant heat component has been transmitted to said fluid conduit, passing the same in regulated quantities around the outer periphery of the upper portion of said chamber whereby to heat. the chamber and maintain the vaporous products therein at a temperature near the maximum attained by the oil in the heating coil, withdrawing vaporous conversion products from the upper portion of the chamber, cooling the same sufficiently to retard any substantial further conversion thereof, introducing the resulting partially cooled products into a reduced pressure vaporizing and separating chamber ywherein separation of their vaporous and non-vaporous components is accomplished, subjecting the vapors to fractionation whereby their components boiling above the range of the desired nal light distillate product of the process are condensed as reflux condensate, subjecting fractionated vapors of the desired endboiling point to condensation and recovering the resulting distillate.

2. A process as claimed in claim 1 wherein charging stock for the process is preheated, prior to its introduction into said fluid conduit, by;

indirect heat exchange with said combustion gases after contact of the latter with said chamber.

products are partially cooled by indirect heat ex-,` change with hydrocarbon oil charging stock for -the process and regulated quantities of the partially cooled reflux condensate are commingled with the stream of vaporous products passing from said heated chamber tothe succeeding vai porizing and separating zone.

5. A process as claimed in claim 1 wherein regulated quantities of the reflux condensate formed by said fractionation of the -vaporous conversion products is partially cooled by indirect heat lexchange with hydrocarbon oil charging stock for theV process and regulated quantities of the partially cooled reiiux condensate are returned to the fractionating stage of the system to assist cooling-and fractionation therein.

6. In .the reforming of light hydrocarbon distillates containing low anti-knock gasoline fractions to enhance the anti-knock value thereof, the

method which comprises passing the low antiknock distillate in a restrlcted stream through a heating coil and heating the same therein to reforming temperature under substantial superatmospherlc pressure, then' introducing the distillate, promptly upon its elevation to reforming temperature, into the lower portion of an en.-

larged vertical soaking chamber maintained under substantially the same pressure as prevails at the outlet qi the coil, said lower portion of the chamber being unheated and there being effected in this unheated portion of the chamber a separation of vapors from residual liquid and heavy polymerization products, externally heatingthe remaining portion of the chamber sufficiently to maintain the vapors therein at or near the maximum temperature attained by Ithe distillate in the coil, removing said liquid and heavy prod-v ucts from the lower portion of the chamber, passing the vapors upwardly through the heated portion of the chamber and retaining them in the chamber for asuiiicient time to effect substantial reforming thereof into high anti-knock gasoline,

ana'oos removing the reformed vapors from the upper portion of the chamber and fraotionating and condensing the same. I

7. In the reforming of light hydrocarbon dist tillates containing low anti-knock gasoline fractions to enhance the anti-knock value thereof, the method which comprises passing the low anti-knock distillate in a restricted stream through a. heating coil and heating the same therein to reforming temperature under substantial superatmospheric pressure, then introducing the distillate promptly upon its elevation to reforming temperature, into the lower portion of an enlarged vertical soaking chamber maintained under substantially the same pressure as prevailsl at the outlet of the coil, said lower portion oi' the chamber being unheated and there being ei'- fected in this unheated portion of the chamber a separation ot vapors from residual liquid and heavy polymerization products, externally heating the remaining portion of the chamber sumciently to maintain the vapors therein at or near the maximum temperature attained by the distillate tial reforming thereof into high anti-knock gaso- 4 line, removing the reformed vapors from the upper portion of the chamber and introducing the same into a vaporizing chamber maintained under substantially lower pressure than the soaking chamber, discharging the liquid products withdrawn from the lower portion of the soaking chamber into said vaporizing chamber; separately removing vapors and residue from the vaporizing chamber and fractionating and condensing the former.

8. The process as dened in claim 1 further characterized in that the liquid products withdrawn from the lower portion of the mst-named chamber are discharged into said reduced presg@ surechamber.

mam 

